High-strength oil casing resistant to co2 and microbial corrosion and manufacturing method therefor

Abstract

The present disclosure provides a high-strength oil casing resistant to CO2 and microbial corrosion and a manufacturing method therefor. The oil casing comprises, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass: C: 0.06-0.20%, Cr: 1.5-7.0%, Cu: 0.3-3.5%, P≤0.015, S≤0.007. For the oil casing of the present disclosure, an oil casing with CO2-SRB-TGB corrosion resistance, a yield strength of ≥758 MPa, preferably ≥800 MPa, and a full-sized impact energy at 0° C. of ≥80J, preferably ≥95J can be obtained by controlling the amounts of Cr and Cu added and the contents of impurity elements P and S, optimizing the proportion of chemical elements, and combining TMCP manufacturing process, controlling the rolling temperature, the temperature before cooling and the cooling rate.

1 . An oil casing, wherein the oil casing comprises, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass: C: 0.06%-0.20%, Cr: 1.5%-7.0%, Cu: 0.3%-3.5%, P≤0.050% and S≤0.010%, preferably P≤0.015% and S≤0.007%. 
     
     
         2 . The oil casing according to  claim 1 , wherein the oil casing further comprises REM in percentage by mass: 0.07%-0.75%, preferably 0.10%-0.75%. 
     
     
         3 . The oil casing according to  claim 2 , wherein the REM comprises one or both of La and Ce, and contents of La and Ce in percentage by mass satisfy the following inequality: 0.07%≤La+Ce≤0.35%, preferably 0.15%≤La+Ce≤0.35%. 
     
     
         4 . The oil casing according to  claim 1 , wherein a Cr content is 3.0-7.0%, preferably 3.0-5.0%; and/or a Cu content is 1.5%-3.5%. 
     
     
         5 . The oil casing according to  claim 1 , wherein the oil casing further comprises the following chemical elements in percentage by mass: Si: 0.1%-1.0%, Mn: 0.10%-2.5%, Ni: 0.5%-3.5%, Mo: 0.1%-3.5%, Nb: 0.02%-0.15%, V: 0.01%-0.20%, Al: 0.01%-0.08%, B: 0.0010%-0.008%. 
     
     
         6 . The oil casing according to  claim 5 , wherein the oil casing satisfies one or more of the following:
 Mn: 0.5-2.5%;   Ni: 1.0-3.5%;   Mo: 1.0-3.5%; and   V: 0.06-0.20%.   
     
     
         7 . The oil casing according to  claim 1 , wherein the oil casing has an average corrosion rate of <0.0250 mm/a and a local corrosion rate of <0.0450 mm/a measured according to ASTM G111-97 (2013) standard. 
     
     
         8 . The oil casing according to  claim 1 , wherein the oil casing has a yield strength of ≥758 MPa, preferably ≥800 MPa, a full-sized impact energy at 0° C. of ≥80 J, preferably ≥95 J; and/or, a microstructure of tempered sorbite. 
     
     
         9 . A method for manufacturing the oil casing according to  claim 1 , wherein the method comprises the following steps:
 S1: performing smelting and casting on molten steel, and then forging or rolling to obtain a pipe blank;   S2: performing heating, heat holding, piercing, continuous-rolling, and stretch reducing or sizing on the pipe blank of step S1, obtaining a pierced billet; wherein a rolling temperature in the continuous-rolling step is 900-970° C.;   S3: cooling the pierced billet of step S2 to room temperature, obtaining an oil casing; preferably, water-cooling the pierced billet of step S2, wherein a temperature of the pierced billet before cooling is ≥870° C. and a cooling rate is 20-60° C./s.   
     
     
         10 . The method according to  claim 9 , wherein in step S2, a temperature of the heating is 1220-1280° C., and a time of the heat holding is 1-4 hours. 
     
     
         11 . The method according to  claim 9 , wherein in step S2, a temperature of the piercing is 1170-1250° C. 
     
     
         12 . The method according to  claim 9 , wherein the method further comprises the following steps:
 S4: performing a tempering heat treatment on the oil casing of step S3, wherein a tempering temperature is 530-630° C. and a holding time is 40-60 minutes.   
     
     
         13 . The method according to  claim 9 , wherein the oil casing further comprises REM in percentage by mass: 0.07%-0.75%, preferably 0.10%-0.75%. 
     
     
         14 . The method according to  claim 13 , wherein the REM comprises one or both of La and Ce, and contents of La and Ce in percentage by mass satisfy the following inequality: 0.07%≤La+Ce≤0.35%, preferably 0.15%≤La+Ce≤0.35%. 
     
     
         15 . The method according to  claim 9 , wherein a Cr content is 3.0-7.0%, preferably 3.0-5.0%; and/or a Cu content is 1.5%-3.5%. 
     
     
         16 . The method according to  claim 9 , wherein the oil casing further comprises the following chemical elements in percentage by mass: Si: 0.1%-1.0%, Mn: 0.10%-2.5%, Ni: 0.5%-3.5%, Mo: 0.1%-3.5%, Nb: 0.02%-0.15%, V: 0.01%-0.20%, Al: 0.01%-0.08%, B: 0.0010%-0.008%. 
     
     
         17 . The method according to  claim 16 , wherein the oil casing satisfies one or more of the following:
 Mn: 0.5-2.5%;   Ni: 1.0-3.5%;   Mo: 1.0-3.5%; and   V: 0.06-0.20%.   
     
     
         18 . The method according to  claim 9 , wherein the oil casing has an average corrosion rate of <0.0250 mm/a and a local corrosion rate of <0.0450 mm/a measured according to ASTM G111-97 (2013) standard. 
     
     
         19 . The method according to  claim 9 , wherein the oil casing has a yield strength of ≥758 MPa, preferably ≥800 MPa, a full-sized impact energy at 0° C. of ≥80 J, preferably ≥95 J; and/or, a microstructure of tempered sorbite.